During vehicle travel there are many instances where the vehicle must stop and idle while still remaining in gear. For example, vehicles stop and idle at traffic signals, cross-walks, stop signs, and the like. During idle conditions when the transmission is in gear, transmission neutral idle control can be used to improve fuel economy by reducing the load on the engine. When the vehicle is at rest, the brakes are applied, the transmission is in a drive manual range, and the engine is idling, a transmission drive input clutch can be released to produce a geared neutral state. By going to this geared neutral state, the amount of fuel required to keep the engine idle stable will be reduced when compared to normal in-gear idle conditions. This is intended to improve fuel economy during conditions that would be encountered during urban driving when the vehicle frequently stops for traffic lights, or during congested stop-and-go driving.
Vehicles implementing the neutral idle control may experience vehicle roll-back events during periods of idle while positioned on a hill. More specifically, if a vehicle is idling on a surface that has a sufficient grade, the vehicle may be induced to roll backward once the transmission input clutch is released. This occurs when the brake pressure is not sufficient to maintain the position of the vehicle.